The agency, which insured nearly a third of new mortgages in 2009, will increase the premium it charges for its mortgage insurance and require those with weaker credit scores to come up with larger downpayments.

The FHA will also reduce the amount of money a seller can provide a homebuyer for closing costs, as well as tighten its enforcement of lenders.

"Striking the right balance between managing the FHA's risk, continuing to provide access to underserved communities, and supporting the nation's economic recovery is critically important," FHA Commissioner David Stevens said in a statement. "Importantly, FHA will remain the largest source of home purchase financing for underserved communities."

FHA loans have skyrocketed in popularity during the mortgage crisis since the agency backstops banks if borrowers stop paying. But housing experts are growing increasingly concerned about the agency's ability to handle rising numbers of defaults. (Cash cushion shrivels for FHA.)

In November, the agency reported that its reserve fund has dropped to .53% of its insurance guarantees, well below the 2% ratio mandated by Congress and the 3% ratio it had last fall. The fund covers losses on the mortgages the agency insures.

Federal housing officials, who took several steps to shore up the agency's finances last year, promised to do more at a congressional hearing in December. The new announcement is the latest set of changes to FHA policies.

What the new rules mean

FHA is making these changes in order to bring its reserve fund up back up to the 2% ratio, Stevens said in a conference call with reporters. However, the agency also wants to make sure that the new rules don't disrupt the housing market and don't hurt FHA's ability to assist the underserved.

The agency will increase its up-front mortgage insurance premium to 2.25%, from 1.75%. It will also ask Congress for the right to hike its ongoing premium, currently as much as .55% monthly. The agency will then shift some of the increase in the up-front premium to the ongoing charge.

Raising the premium is the best way to add to the reserve fund, Stevens said.

The move isn't likely to hurt borrowers much, said Thomas Lawler, founder of Lawler Economic & Housing Consulting. Most homebuyers will likely finance it so it will only bump up their monthly payments by a little.

"This doesn't increase the amount they need to bring to the closing table," Lawler said.

The FHA will also require borrowers to have at least a credit score of 580 to qualify for the agency's 3.5% downpayment program. Those with lower scores will have to pay at least 10%. However, this rule may have little practical effect since Stevens recently said the average borrower score is 693.

The new policy also will reduce the amount of money sellers can provide to homebuyers at closing to 3%, down from 6%, of the home's price. That change will bring the agency in line with industry standards and remove the incentive to inflate appraisals.

Finally, officials plan to clamp down on lenders offering FHA mortgages. The agency will more closely monitor their performance, as well as seek legislative authority to require mortgage firms to assume liability for all loans they originate and underwrite.It will also publicly report lender performance data.

One thing the agency did not do is to broadly increase the downpayment requirement. Many industry observers said such a step is necessary to reduce FHA loans' high delinquency rates. Borrowers with little equity in their homes are more likely to default or walk away.

The agency has seen a spike in delinquencies amid the mortgage meltdown. Some 14.36% of FHA loans were past due in the third quarter, according to the Mortgage Bankers Association. This compares to 9.64% of all loans.

"They are not addressing the fundamental issue -- that FHA loans are too risky," said real estate finance consultant Edward Pinto, former chief credit officer for Fannie Mae (FNM, Fortune 500) in the late 1980s. Borrowers "need more skin in the game."

FHA did not increase minimum downpayments more broadly because its borrowers with credit scores above 580 were generally timely with their payments.

"The reason why we drew the line at 580 is that there are clear performance drop offs as you drop down credit score tiers," Stevens said.

Agency plays crucial role

As banks have clamped down on mortgage lending, the FHA program has emerged as one of the few ways people can buy a home.

Banks are more willing to make FHA loans because they come with a federal guarantee to cover losses if the borrower defaults. And borrowers can more easily qualify for FHA loans because they only need 3.5% down and can have lower credit scores.

As a result, demand for FHA loans has exploded. The agency guaranteed more than $360 billion in single-family mortgages in fiscal 2009, which ended Sept. 30, more than four times the volume in 2007.

The agency insured about 30% of home purchases and 20% of refinanced mortgages in 2009. Nearly 50% of first-time homebuyers go through the agency.